Jacobian Parameters structure

Orekit usage
1

Hi all,

I had a hopefully quick question on how the Jacobian parameters matrix is built and how the order of the columns is defined. I define the following matrix:

double [][] jacobianParam = new double[JacobiansMapper.STATE_DIMENSION][mapper.getParameters()];
mapper.getParametersJacobian(nextStepState, jacobianParam);

Let’s say I set up three parameters drivers:

	if (fm.isSupported("ParameterA")) {
		fm.getParameterDriver("ParameterA").setSelected(true);
	}
	if (fm.isSupported("ParameterC")) {
		fm.getParameterDriver("ParameterC").setSelected(true);
	}
	if (fm.isSupported("ParameterB")) {
		fm.getParameterDriver("ParameterB").setSelected(true);
	}
}

I end up with a 6x3 Jacobian parameters matrix. But how did the function picked which column would correspond to each parameter?

When using it I first assumed it was in the order I was selecting them (in my case it would have been A/C/B) but then I faced some issues and was under the impression that it was only sorted in alphabetical order (A/B/C), is that correct?

Thank you very much for the information!

Kind regards,

B.

2

Hi,

The estimated force model parameters are sorted in alphabetical order. This step is performed in PartialDerivativesEquations.freezeParametersSelection() method.

            // third pass: sort parameters lexicographically
            selected.sort();

Kind regards,
Bryan

3

Thank you very much for the very clear answer!

Kind regards,

B.

4

I am sorry @benoist , I made a mistake last time. I edited my post with the correct answer.

Bryan